Cracking the SAT Physics Subject Test

In this case, then, if V denotes the voltage drop across the combination, we have This idea can be applied to any number of resi ...

circuit the current is the same through each resistor. In parallel, the voltage drop is the same. So if V is the voltage drop ac ...

Notice that the equation for the equivalent resistance for resistors in series is just like the equation for the equivalent capa ...

This resistance is in series with the 4 Ω resistor, so the overall equivalent resistance in the circuit is Requiv = 4 Ω + 2 Ω = ...

Here’s How to Crack It You might want to redraw the circuit each time we replace a combination of resistors by its equivalent re ...

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From diagram , which has just one resistor, we can figure out the current. Now we can work our way back to the original circuit ...

Resistors in parallel share the same voltage drop. So we take the voltage drop, V = 4 V, back to diagram. The voltage drop acros ...

For the 4 Ω resistor: P = IV = (2 A)(8 V) = 16 W For the 3 Ω resistor: P = IV = ( A)(4V) = W For the 6 Ω resistor: P = IV = ( A) ...

In which direction will current flow and why? What’s the overall emf? What’s the current in the circuit? At what rate is energy ...

Charges forced through ε 1 will lose, rather than gain, 4 V of potential, so the overall emf of this circuit is ε 2 − ε 1 = 8 ...

Here’s How to Crack It Before the switch is closed, there is no complete conducting pathway from the positive terminal of the ba ...

In this case, a distinction can be made between the emf of the battery and the actual voltage it provides once the current has b ...

resistors in parallel will create the smallest resistance and draw the greatest total current. In this case, the equivalent resi ...

and the total current is I = = 9 A. (You could verify that 3 A of current would flow in each of the three branches of the combin ...

Here’s How to Crack It Assume that the ammeter is ideal; it has negligible resistance and doesn’t alter the current that it’s tr ...

this current splits. Since R 1 is twice R 2 , half as much current will flow through R 1 as through R 2 ; the current through R ...

RP is in series with R 3 , so the equivalent resistance is Reqiv = RP + R 3 = (2 Ω) + (8 Ω) = 10 Ω and the current that flows th ...

COMBINATIONS OF CAPACITORS When a capacitor charges up, work must be done by an external force (for example a battery). This inc ...

so CP = C 1 + C 2 which can be extended to more than 2 capacitors. So the equivalent capacitance of a collection of capacitors i ...